About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Abstract

Wide field-of-view gigapixel imaging systems capable of diffraction-limited resolution and video-rate acquisition have a broad range of applications, including sports event broadcasting, security surveillance, astronomical observation, and bioimaging. The complexity of the system integration of such devices demands precision optical components that are fully characterized and qualified before being integrated into the final system. In this work, we present component and assembly level characterizations of microcameras in our first gigapixel camera, the AWARE-2. Based on the results of these measurements, we revised the optical design and assembly procedures to construct the second generation system, the AWARE-2 Retrofit, which shows significant improvement in image quality.

Figures (8)

(a) Optical design principle of AWARE-2 camera. 3D renderings of (b) AWARE-2 microcamera and (c) AWARE-2 Retrofit microcamera discussed in this work. See the main text for the optical design differences between the two microcameras. The internal structures of the barrels are shown for illustration. Baffles that cut off unnecessary stray light is effectively implemented by minimizing the lens apertures and the inner diameter of the barrel.

Image sensor MTF characterization. (a) Experimental setup to measure the sensor MTF. (b) The experimental MTF of monochromatic (red) and color (blue) image sensors measured with broadband light source as a function of spatial frequency in units of line pairs per mm (lp/mm). The shade illustrates uncertainty of the experiment, obtained from repetition of the experiment. (c) and (d) show typical MTF measurements as a function of wavelength for monochromatic and color sensors, respectively.

Fringe pattern images of prototype lenses. (a) A molded lens with less birefringent plastic material, OKP4. The white circles indicate the outer edge of the lens and the designed clear aperture. The arrow indicates the thermal stress that occurred at the gate during the injection molding process, located outside the designed aperture. (b) A glass lens used in the AWARE-2 Retrofit microcamera, showing no visible fringe. The color bar indicates the pixel value in the images.

Surface form measurements and MTF simulation of the measured surface. (a) Comparison of the experimental profile with the nominal design. (b) Surface model with fit parameters, C and K to obtain the realistic representation of the measured lens. Note that 2D plots in (a) and (b) were obtained by taking the cross-section of the 3D surface with the x–z plane. (c) Simulated MTF (black dots) impacted by surface deviation of the prototype lens, plotted together with the MTF for the nominal design (red line) and the diffraction-limited curve (dashed line).

(a) Test jig used to test AWARE-2 and AWARE-2 Retrofit microcameras. Broadband light source is filtered by a bandpass filter at 590 nm in order to minimize the chromatic aberrations and illuminates the test target placed at the nominal object plane of the microcamera under test. The ground-glass diffuser inserted after the bandpass filter provides uniform illumination. (b) Image of the 1951 USAF resolution test chart, normalized by the maximum pixel value, taken with the AWARE-2 microcamera. Stray light creates a bright ring at the edge of the field (cross-section shown by the red trace in the inset), and reduces the contrast across the image of a dark object (black trace in the inset). (c) Normalized image of the Imatest spatial frequency response (SFR) chart taken with the AWARE-2 Retrofit microcamera. The cross-sections in the inset shows absence of bright artifact ring (red trace), and a much higher contrast (black trace).

(a) A color map of spatial frequency at MTF 20% measured in a typical AWARE-2 Retrofit microcamera at optimal focus. The plot was generated by linearly interpolating the experimental data (circles) of spatial frequencies at 20% of the MTF. The data points in black (white) circles are measured from vertical (horizontal) slanted edges. (b) Measured MTF curves at the best (green dots) and worst (orange dots) optical performance, corresponding to location 1 and 2 shown in (a), respectively.